Spitfire7856

I have a Giles 202 with a Brillelli 26cc gasser on the business end and it was doing the same thing. It would run great on the ground and just as soon as it lifted off it would sag. In my case it turned out that the engine was fine, it was the air flow off of the cowl that was causing the problem. I installed a copper 90 degree elbow in the plastic vilocity stack so the opening was facing forward and that stopped all the problems.